Design of internal combustion engine systems involves developing thermal management systems for controlling various subsystems of an internal combustion engine system. One parameter of concern is vehicle fuel economy, which can be influenced b the temperature of engine system components. These components can include the engine, transmission and other powertrain components, and exhaust aftertreatment systems components, which generally operate more efficiently after achieving a sufficient operating temperature after a warm up period.
Generally, efficiency peaks when the system component temperatures reach a particular point. A system that is either too cold or too warm will demonstrate degraded efficiency as compared to a system in the neighborhood of the temperature “sweet spot.” Traditionally, engine systems and other powertrain components are isolated in the treatment of powertrain warm up. Engine calibrations often provide for “cold calibration” functioning that is primarily targeted at preventing misfire and maintaining emissions control rather than addressing fuel economy.
In aftertreatment systems, two stages of thermal management that often cost the system from the standpoint of fuel consumption are selective catalytic reduction (SCR) warm-up and diesel particulate filter (DPF) regeneration. These two stages of aftertreatment system component thermal management also aid to warm-up a diesel oxidation catalyst (DOC) to light-off temperature. At light-off temperature the diesel fuel present in the DOC will ignite, yielding an exothermic reaction with a consequent increase in exhaust gas temperature.
Currently, engine systems and other powertrain components are isolated in the treatment of aftertreatment system thermal management. Engine calibrations often provide for “regeneration calibration” and “warm-up calibration” for the aftertreatment system. For example, a “DOC warm-up calibration” can include injecting late post fuel that combusts in-cylinder sufficiently late in the piston cycle to primarily produce heat and little or no torque.